Troubles due to low elasticity of the hair (for example, low tension, poor firmness and less bulkiness) amount to a considerable part in problems on the hair. In order to satisfy the requirements by those having these troubles, there have been marketed a number of hair treatment compositions containing elasticity imparting components and conditioning components. However, these components are adsorbed on the surface of the hair to thereby exert the desired effects. Since these components are washed away upon shampooing, it is needed to apply them repeatedly, which requires trouble some procedures. On the other hand, attempts have been made to penetrate active components into the hair so as to achieve the desired effects. For example, there has been reported a method for treating the hair with an aqueous solution of naphthalenesulfonic acid [refer to J. Soc. Cosmet. Chem., 36, 87-99 (1985)]. However, since the naphthalenesulfonic acid cannot sufficiently penetrate into the hair, a long time is required for the completion of the treatment, and this method cannot give any satisfactory effect.